Polymer flake degassing system and methods

ABSTRACT

Systems and methods for improved degassing of polymer flake are provided herein. These systems include a polymerization reactor configured to polymerize one or more olefin monomers and produce a product stream comprising solid polymer flake entrained in a fluid; a flash chamber configured to separate the solid polymer flake from the fluid and to produce a fluid stream and a concentrated stream; and a first degassing chamber configured to separate the concentrated stream by contacting the concentrated stream with a purge fluid comprising one or more light hydrocarbons to produce a partially degassed polymer flake stream and a purge fluid stream.

CROSS-REFERENCE TO RELATED APPLICATIONS

None.

TECHNICAL FIELD OF THE DISCLOSURE

This application relates to systems and processes for degassing of solidpolymer flake.

BACKGROUND

Production of solid polymer flake in a fluid requires downstreamseparation of the fluid from the polymer flake. Polymer degassingsystems are known, but typically require the use of high volumes ofnitrogen to remove the fluid, for example, hydrocarbons, from the solidpolymer flake. Nitrogen gas quickly becomes saturated with hydrocarbons,which are typically a major component of the fluid in which the solidpolymer flake is entrained. Because nitrogen becomes saturated soquickly, large volumes of nitrogen gas are required to effectivelyremove the fluid from the solid polymer flake. Further, additionalseparation processes are typically needed to separate the fluid from thenitrogen gas, so that the separated nitrogen and fluid can be recycledto the polymer production process. These processes add significantadditional cost and complexity to the process.

Accordingly, improved systems and methods for improved polymer degassingare needed.

SUMMARY

This summary is provided to introduce various concepts in a simplifiedform that are further described below in the detailed description. Thissummary is not intended to identify required or essential features ofthe claimed subject matter nor is the summary intended to limit thescope of the claimed subject matter.

This summary and the following detailed description provide examples andare explanatory only of the invention. Accordingly, the foregoingsummary and the following detailed description should not be consideredto be restrictive. Additional features or variations thereof can beprovided in addition to those set forth herein, such as for example,various feature combinations and sub-combinations of these described inthe detailed description.

In one aspect, a system for polymerizing one or more olefin monomers isprovided, the system including: a polymerization reactor configured topolymerize one or more olefin monomers and produce a product streamincluding solid polymer flake entrained in a fluid; a flash chamberconfigured to separate the solid polymer flake from the fluid and toproduce a fluid stream and a concentrated stream, wherein the fluidstream includes the solid polymer flake in a lower concentration than inthe product stream and the concentrated stream includes the solidpolymer flake in a higher concentration than in the product stream; afirst degassing chamber configured to separate the concentrated streamby contacting the concentrated stream with a purge fluid including oneor more light hydrocarbons to produce a partially degassed polymer flakestream and a purge fluid stream, wherein the partially degassed polymerflake stream includes the fluid in a lower concentration than in theconcentrated stream and the purge fluid stream includes the solidpolymer flake in a lower concentration than in the concentrated stream.

In another aspect, a process for polymerizing one or more olefinmonomers is provided, the process including: polymerizing one or moreolefin monomers in a polymerization reactor to form a product streamincluding solid polymer flake entrained in a fluid; passing the productstream to a flash chamber to produce a fluid stream and a concentratedstream of polymer flake entrained in the fluid, wherein the fluid streamincludes the solid polymer flake in a lower concentration than in theproduct stream and the concentrated stream includes the solid polymerflake in a higher concentration than in the product stream; passing theconcentrated stream to a first degassing chamber, wherein a first purgefluid including one or more light hydrocarbons contacts the concentratedstream to produce a partially degassed polymer flake stream and a purgefluid stream wherein the partially degassed polymer flake streamincludes the fluid in a lower concentration than in the concentratedstream and the purge fluid stream comprises the solid polymer flake in alower concentration than in the concentrated stream.

These and other aspects and aspects according to this disclosure areprovided in the drawings, detailed description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures form part of the present specification and areincluded to further demonstrate certain aspects of the presentdisclosure. The invention may be better understood by reference to oneor more of these figures in combination with the detailed description ofspecific aspects presented herein.

FIG. 1 is a schematic illustration of a system or process according toaspects of the present disclosure.

DEFINITIONS

The following definitions are provided in order to aid those skilled inthe art in understanding the detailed description of the presentinvention. Unless otherwise defined herein, scientific and technicalterms used in connection with the present invention shall have themeanings that are commonly understood by those of ordinary skill in theart to which this invention belongs, and unless otherwise indicated orthe context requires otherwise, these definitions are applicablethroughout this disclosure. Further, unless otherwise required bycontext, singular terms shall include pluralities and plural terms shallinclude the singular. For example, if a term is used in this disclosurebut is not specifically defined herein, the definition from the IUPACCompendium of Chemical Terminology, 2nd Ed (1997) can be applied, aslong as that definition does not conflict with any other disclosure ordefinition applied herein, or render indefinite or non-enabled any claimto which that definition is applied. To the extent that any definitionor usage provided by any document incorporated herein by referenceconflicts with the definition or usage provided herein, the definitionor usage provided herein controls.

Unless explicitly stated otherwise in defined circumstances, allpercentages, parts, ratios, and like amounts used herein are defined byweight.

Further, in this connection, certain features of the invention whichare, for clarity, described herein in the context of separate aspects,may also be provided in combination in a single aspect. Conversely,various features of the invention that are, for brevity, described inthe context of a single aspect, may also be provided separately or inany sub-combination.

Regarding claim transitional terms or phrases, the transitional term“comprising”, which is synonymous with “including”, “containing”, or“characterized by” is inclusive or open-ended and does not excludeadditional, un-recited elements or method steps. The transitional phrase“consisting of” excludes any element, step, or ingredient not specifiedin the claim. The transitional phrase “consisting essentially of” limitsthe scope of a claim to the specified materials or steps and those thatdo not materially affect the basic and novel characteristic(s) of theclaimed invention. A “consisting essentially of” claim occupies a middleground between closed claims that are written in a “consisting of”format and fully open claims that are drafted in a “comprising” format.Absent an indication to the contrary, when describing a compound orcomposition “consisting essentially of” is not to be construed as“comprising,” but is intended to describe the recited component thatincludes materials which do not significantly alter composition ormethod to which the term is applied. For example, a feedstock consistingessentially of a material A can include impurities typically present ina commercially produced or commercially available sample of the recitedcompound or composition. When a claim includes different features and/orfeature classes (for example, a method step, feedstock features, and/orproduct features, among other possibilities), the transitional termscomprising, consisting essentially of, and consisting of, apply only tothe feature class to which is utilized and it is possible to havedifferent transitional terms or phrases utilized with different featureswithin a claim. For example, a method can comprise several recited steps(and other non-recited steps) but utilize a catalyst system preparationconsisting of specific steps and utilize a catalyst system comprisingrecited components and other non-recited components. While compositionsand methods are described in terms of “comprising” various components orsteps, the compositions and methods can also “consist essentially of” or“consist of” the various components or steps.

The articles “a” and “an” may be employed in connection with variouselements and components of compositions, processes or structuresdescribed herein. This is merely for convenience and to give a generalsense of the compositions, processes or structures. Such a descriptionincludes “one or at least one” of the elements or components. Moreover,as used herein, the singular articles also include a description of aplurality of elements or components, unless it is apparent from aspecific context that the plural is excluded.

“Optional” or “optionally” means that the subsequently described eventor circumstance can or cannot occur, and that the description includesinstances where the event or circumstance occurs and instances where itdoes not.

As used herein, “light hydrocarbons” is used to refer to hydrocarbonshaving 3 or fewer carbon atoms, and hydrocarbons which are gases at 1atm and 70° F. For example, “light hydrocarbons” include methane,ethane, ethylene, propane, isopropane, propylene, isopropylene, and thelike.

As used herein, “heavy hydrocarbons” is used to refer to hydrocarbonshaving 4 or more carbon atoms. For example, “heavy hydrocarbons” includebutane, isobutene, butene, pentane, pentene, hexane, hexane,cyclohexane, octane, octane, benzene, styrene, and the like. Throughoutthis specification, “heavy hydrocarbons” may be abbreviated “HHC.”

As used herein, “interstitial gas” is used to refer to the gas betweenpolymer flake particles in a partially degassed stream, a completelydegassed stream, or a settled sample of solid polymer flake.

As used herein, “solid polymer flake” is used to refer to polymer flakewhich has a solid exterior, regardless of whether the interior of thepolymer flake is a solid or fluid. By “solid exterior,” it is intendedto reflect that the polymer flake maintains its shape in the processconditions.

As used herein, “degassing” is used broadly to refer to the process ofremoving a fluid from solid polymer flake or separating a fluid fromsolid polymer flake, regardless of whether the fluid is a liquid or agas.

As used herein, “minimum fluidization velocity” is used broadly to referto the minimum velocity of a fluid necessary to fluidize solidparticles.

The terms “configured for use” or “adapted for use” and similar languageis used herein to reflect that the particular recited structure orprocedure is used in a system or process as disclosed herein. Forexample, unless otherwise specified, a particular structure “configuredfor use” means it is “configured for use in a reactor system”, includingfor example, “configured for use in an olefin polymerization reactorsystem” and therefore is designed, shaped, arranged, constructed, and/ortailored to effect olefin polymerization, as would have been understoodby the skilled person.

The term “olefin” is used herein in accordance with the definitionspecified by IUPAC: acyclic and cyclic hydrocarbons having one or morecarbon-carbon double bonds apart from the formal ones in aromaticcompounds. The class “olefins” subsumes alkenes and cycloalkenes and thecorresponding polyenes. Ethylene, propylene, 1-butene, 2-butene,1-hexene and the like are non-limiting examples of olefins.

The term “about” means that amounts, sizes, formulations, parameters,and other quantities and characteristics are not and need not be exact,but may be approximate and/or larger or smaller, as desired, reflectingtolerances, conversion factors, rounding off, measurement error and thelike, and other factors known to those of skill in the art. In general,an amount, size, formulation, parameter or other quantity orcharacteristic is “about” or “approximate” whether or not expresslystated to be such. The term “about” also encompasses amounts that differdue to different equilibrium conditions for a composition resulting froma particular initial mixture. Whether or not modified by the term“about”, the claims include equivalents to the quantities. The term“about” may mean within 10% of the reported numerical value, or within5% of the reported numerical value, or within 2% of the reportednumerical value.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having,” “contains” or “containing,” or any othervariation thereof, are intended to cover a non-exclusive inclusion. Forexample, a composition, a mixture, process, method, article, orapparatus that comprises a list of elements is not necessarily limitedto only those elements but may include other elements not expresslylisted or inherent to such composition, mixture, process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

DETAILED DESCRIPTION

The FIGURES described above and the written description of specificstructures and functions below are not presented to limit the scope ofwhat Applicants have invented or the scope of the appended claims.Rather, the Figures and written description are provided to teach anyperson skilled in the art to make and use the inventions for whichpatent protection is sought. Those skilled in the art will appreciatethat not all features of a commercial aspect of the inventions aredescribed or shown for the sake of clarity and understanding. Persons ofskill in this art will also appreciate that the development of an actualcommercial aspect incorporating aspects of the present inventions willrequire numerous implementation-specific decisions to achieve thedeveloper's ultimate goal for the commercial aspect. Suchimplementation-specific decisions may include, and likely are notlimited to, compliance with system-related, business-related,government-related and other constraints, which may vary by specificimplementation, location and from time to time. While a developer'sefforts might be complex and time-consuming in an absolute sense, suchefforts would be, nevertheless, a routine undertaking for those of skillin this art having benefit of this disclosure. It must be understoodthat the inventions disclosed and taught herein are susceptible tonumerous and various modifications and alternative forms. Lastly, theuse of a singular term, such as, but not limited to, “a,” is notintended as limiting of the number of items. Also, the use of relationalterms, such as, but not limited to, “top,” “bottom,” “left,” “right,”“upper,” “lower,” “down,” “up,” “side,” and the like are used in thewritten description for clarity in specific reference to the Figures andare not intended to limit the scope of the invention or the appendedclaims.

Systems and Processes for Polymerizing Olefins

Systems for polymerizing one or more olefin monomers are providedherein. In some aspects, the system includes a polymerization reactorconfigured to polymerize one or more olefin monomers and produce aproduct stream comprising solid polymer flake entrained in a fluid. Forexample, in some aspects the polymerization reactor is a fluidized bedreactor. In some aspects, the polymerization reactor is an autoclavereactor. In some aspects, the polymerization is a tubular reactor.

Processes for polymerizing one or more olefin monomers are providedherein. In some aspects, the process includes polymerizing one or moreolefin monomers in a polymerization reactor to form a product streamcomprising solid polymer flake entrained in a fluid. For example, insome aspects the polymerization reactor is a fluidized bed reactor. Insome aspects, the polymerization reactor is an autoclave reactor. Insome aspects, the polymerization is a tubular reactor.

In some aspects, the solid polymer flake exiting the polymerizationreactor is at a temperature of from about 150° F. to about 190° F., forexample about 150° F., about 155° F., about 160° F., about 165° F.,about 170° F., about 175° F., about 180° F., about 185° F., about 190°F., or any ranges therebetween. In some aspects, the maximum temperatureof the solid polymer flake is the melting point of the solid polymerflake. In some aspects, the maximum temperature of the solid polymerflake is the minimum sintering temperature of the solid polymer flake.In some aspects, the solid polymer flake is at a temperature which isfrom about 15° C. to about 40° C. lower than the melting temperature ofthe solid polymer flake, for example about 15° C. lower, about 20° C.lower, about 25° C. lower, about 30° C. lower, about 35° C. lower, about40° C. lower, or any ranges therebetween.

In some aspects, the one or more olefins include ethylene and thepolymer flake includes polyethylene. In some aspects, the one or moreolefins include propylene and the polymer flake includes polypropylene.In some aspects, the one or more olefins include ethylene and propyleneand the polymer flake includes a co-polymer of ethylene and propylene.In some aspects, the one or more olefins include ethylene and 1-buteneand the polymer flake includes a co-polymer of ethylene and 1-butene. Insome aspects, the one or more olefins include ethylene and 1-hexene, andthe polymer flake includes a co-polymer of ethylene and 1-hexene. Insome aspects, the one or more olefins include ethylene and 1-octene, andthe polymer flake includes a co-polymer of ethylene and 1-octene. Insome aspects, the one or more olefins include pentene and the polymerflake includes polypentene. In some aspects, the one or more olefinsinclude three of propylene, ethylene, 1-butene, 1-hexene, and 1-octene,and the polymer flake includes a terpolymer.

In some aspects, the polymerization reactor is configured to polymerizethe one or more olefins in the presence of one or more heavyhydrocarbons. In some aspects, the one or more heavy hydrocarbonsinclude butane, isobutane, pentane, hexane, octane, or any combinationsthereof. For example, the polymerization reactor may be configured topolymerize the one or more olefins to form a copolymer of the one ormore olefins and the one or more heavy hydrocarbons. In some aspects,the one or more olefins include ethylene and 1-butene and the polymerflake includes a co-polymer of ethylene and 1-butene. In some aspects,the one or more olefins include ethylene and pentene and the polymerflake includes a co-polymer of ethylene and pentene. In some aspects,the one or more olefins include ethylene and 1-hexene, and the polymerflake includes a co-polymer of ethylene and 1-hexene. In some aspects,the one or more olefins include ethylene and 1-octene, and the polymerflake includes a co-polymer of ethylene and 1-octene.

In some aspects, the system further includes a flash chamber configuredto separate the solid polymer flake from the fluid and to produce afluid stream and a concentrated stream. The fluid stream includes thesolid polymer flake in a lower concentration than in the product streamand the concentrated stream includes the solid polymer flake in a higherconcentration than in the product stream. For example, in some aspectsthe fluid stream contains less than about 5 wt. % solid polymer flake,less than about 1 wt. % solid polymer flake, less than about 0.1 wt. %solid polymer flake, for example about 5 wt. % solid polymer flake,about 4 wt. % solid polymer flake, about 3 wt. % solid polymer flake,about 2 wt. % solid polymer flake, about 1 wt. % solid polymer flake,about 0.9 wt. % solid polymer flake, about 0.8 wt. % solid polymerflake, about 0.7 wt. % solid polymer flake, about 0.6 wt. % solidpolymer flake, about 0.5 wt. % solid polymer flake, about 0.4 wt. %solid polymer flake, about 0.3 wt. % solid polymer flake, about 0.2 wt.% solid polymer flake, about 0.1 wt. % solid polymer flake, about 0.09wt. % solid polymer flake, about 0.08 wt. % solid polymer flake, about0.07 wt. % solid polymer flake, about 0.06 wt. % solid polymer flake,about 0.05 wt. % solid polymer flake, about 0.04 wt. % solid polymerflake, about 0.03 wt. % solid polymer flake, about 0.02 wt. % solidpolymer flake, about 0.01 wt. % solid polymer flake, and any rangestherebetween. In some aspects, the concentrated stream contains morethan about 80 wt. % solid polymer flake, more than about 90 wt. % solidpolymer flake, or more than about 95 wt. % solid polymer flake, forexample about 80 wt. % solid polymer flake, about 81 wt. % solid polymerflake, about 82 wt. % solid polymer flake, about 83 wt. % solid polymerflake, about 84 wt. % solid polymer flake, about 85 wt. % solid polymerflake, about 86 wt. % solid polymer flake, about 87 wt. % solid polymerflake, about 88 wt. % solid polymer flake, about 89 wt. % solid polymerflake, about 90 wt. % solid polymer flake, about 91 wt. % solid polymerflake, about 92 wt. % solid polymer flake, about 93 wt. % solid polymerflake, about 94 wt. % solid polymer flake, about 95 wt. % solid polymerflake, about 96 wt. % solid polymer flake, about 97 wt. % solid polymerflake, about 98 wt. % solid polymer flake, about 99 wt. % solid polymerflake, and any ranges therebetween. In some aspects, the fluid is aliquid and the product stream contains from about 30 wt. % solid polymerflake to about 50 wt. % solid polymer flake, for example about 30 wt. %solid polymer flake, about 35 wt. % solid polymer flake, about 40 wt. %solid polymer flake, about 45 wt. % solid polymer flake, about 50 wt. %solid polymer flake, or any ranges therebetween. In some aspects, thefluid is a gas and the product stream contains from about 75 wt. % solidpolymer flake to about 95 wt. % polymer flake, for example about 75 wt.% solid polymer flake, about 80 wt. % solid polymer flake, about 85 wt.% solid polymer flake, about 90 wt. % solid polymer flake, about 95 wt.% solid polymer flake, and any ranges therebetween. When determining theweight percent of a stream which is solid polymer flake or fluid asdescribed herein, any fluid adsorbed to the solid polymer flake isconsidered fluid weight, rather than solid polymer flake weight. In someaspects, the fluid stream includes a mixture of gas and liquid. In someaspects, the fluid stream is a gas. In some aspects, the fluid stream isa liquid. In some aspects, the fluid comprises at least one of the oneor more olefin monomers. In some aspects, the fluid is a gas. In someaspects, the fluid is a liquid. In some aspects, the polymerizationreactor is a gas phase reactor. In some aspects, the polymerizationreactor is a liquid phase reactor, for example a loop slurry reactor oran autoclave reactor.

In some aspects, the process further includes passing the product streamto a flash chamber to produce a fluid stream and a concentrated streamof polymer flake entrained in the fluid. In some aspects, the fluidstream includes the solid polymer flake in a lower concentration than inthe product stream and the concentrated stream includes the solidpolymer flake in a higher concentration than in the product stream. Forexample, in some aspects the fluid stream contains less than about 5 wt.% solid polymer flake, less than about 1 wt. % solid polymer flake, lessthan about 0.1 wt. % solid polymer flake, for example about 5 wt. %solid polymer flake, about 4 wt. % solid polymer flake, about 3 wt. %solid polymer flake, about 2 wt. % solid polymer flake, about 1 wt. %solid polymer flake, about 0.9 wt. % solid polymer flake, about 0.8 wt.% solid polymer flake, about 0.7 wt. % solid polymer flake, about 0.6wt. % solid polymer flake, about 0.5 wt. % solid polymer flake, about0.4 wt. % solid polymer flake, about 0.3 wt. % solid polymer flake,about 0.2 wt. % solid polymer flake, about 0.1 wt. % solid polymerflake, about 0.09 wt. % solid polymer flake, about 0.08 wt. % solidpolymer flake, about 0.07 wt. % solid polymer flake, about 0.06 wt. %solid polymer flake, about 0.05 wt. % solid polymer flake, about 0.04wt. % solid polymer flake, about 0.03 wt. % solid polymer flake, about0.02 wt. % solid polymer flake, about 0.01 wt. % solid polymer flake,and any ranges therebetween. In some aspects, the concentrated streamcontains more than about 80 wt. % solid polymer flake, more than about90 wt. % solid polymer flake, or more than about 95 wt. % solid polymerflake, for example about 80 wt. % solid polymer flake, about 81 wt. %solid polymer flake, about 82 wt. % solid polymer flake, about 83 wt. %solid polymer flake, about 84 wt. % solid polymer flake, about 85 wt. %solid polymer flake, about 86 wt. % solid polymer flake, about 87 wt. %solid polymer flake, about 88 wt. % solid polymer flake, about 89 wt. %solid polymer flake, about 90 wt. % solid polymer flake, about 91 wt. %solid polymer flake, about 92 wt. % solid polymer flake, about 93 wt. %solid polymer flake, about 94 wt. % solid polymer flake, about 95 wt. %solid polymer flake, about 96 wt. % solid polymer flake, about 97 wt. %solid polymer flake, about 98 wt. % solid polymer flake, about 99 wt. %solid polymer flake, and any ranges therebetween. In some aspects, thefluid is a liquid and the product stream contains from about 30 wt. %solid polymer flake to about 50 wt. % solid polymer flake, for exampleabout 30 wt. % solid polymer flake, about 35 wt. % solid polymer flake,about 40 wt. % solid polymer flake, about 45 wt. % solid polymer flake,about 50 wt. % solid polymer flake, or any ranges therebetween. In someaspects, the fluid is a gas and the product stream contains from about75 wt. % solid polymer flake to about 95 wt. % polymer flake, forexample about 75 wt. % solid polymer flake, about 80 wt. % solid polymerflake, about 85 wt. % solid polymer flake, about 90 wt. % solid polymerflake, about 95 wt. % solid polymer flake, and any ranges therebetween.When determining the weight percent of a stream which is solid polymerflake or fluid as described herein, any fluid adsorbed to the solidpolymer flake is considered fluid weight, rather than solid polymerflake weight. In some aspects, the fluid stream includes a mixture ofgas and liquid. In some aspects, the fluid stream is a gas. In someaspects, the fluid stream is a liquid. In some aspects, the fluidcomprises at least one of the one or more olefin monomers. In someaspects, the fluid is a gas. In some aspects, the fluid is a liquid. Insome aspects, the polymerization reactor is a gas phase reactor. In someaspects, the polymerization reactor is a liquid phase reactor, forexample a loop slurry reactor or an autoclave reactor.

In some aspects, the system further includes a first degassing chamberconfigured to separate the concentrated stream by contacting theconcentrated stream with a purge fluid comprising one or more lighthydrocarbons to produce a partially degassed polymer flake stream and apurge fluid stream. The partially degassed polymer flake stream includesthe fluid in a lower concentration than in the concentrated stream andthe purge fluid stream includes the solid polymer flake in a lowerconcentration than in the concentrated stream. In some aspects, thepartially degassed polymer flake stream contains less than 1 wt. %fluid, less than about 0.1 wt. % fluid, or less than about 0.01 wt. %fluid, for example about 1 wt. % fluid, about 0.9 wt. % fluid, about 0.8wt. % fluid, about 0.7 wt. % fluid, about 0.6 wt. % fluid, about 0.5 wt.% fluid, about 0.4 wt. % fluid, about 0.3 wt. % fluid, about 0.2 wt. %fluid, about 0.1 wt. % fluid, about 0.09 wt. % fluid, about 0.08 wt. %fluid, about 0.07 wt. % fluid, about 0.06 wt. % fluid, about 0.05 wt. %fluid, about 0.04 wt. % fluid, about 0.03 wt. % fluid, about 0.02 wt. %fluid, about 0.01 wt. % fluid, or any ranges therebetween. In someaspects, the purge fluid stream contains less than 1 wt. % solid polymerflake, or less than 0.1 wt. % solid polymer flake, for example about 1wt. % solid polymer flake, about 0.9 wt. % solid polymer flake, about0.8 wt. % solid polymer flake, about 0.7 wt. % solid polymer flake,about 0.6 wt. % solid polymer flake, about 0.5 wt. % solid polymerflake, about 0.4 wt. % solid polymer flake, about 0.3 wt. % solidpolymer flake, about 0.2 wt. % solid polymer flake, about 0.1 wt. %solid polymer flake, about 0.09 wt. % solid polymer flake, about 0.08wt. % solid polymer flake, about 0.07 wt. % solid polymer flake, about0.06 wt. % solid polymer flake, about 0.05 wt. % solid polymer flake,about 0.04 wt. % solid polymer flake, about 0.03 wt. % solid polymerflake, about 0.02 wt. % solid polymer flake, about 0.01 wt. % solidpolymer flake, or any ranges therebetween. In some aspects, the purgefluid stream contains at least 0.1 wt. % fluid or at least 1 wt. %fluid, for example about 0.1 wt. % fluid, about 0.5 wt. % fluid, about 1wt. % fluid, about 5 wt. % fluid, about 10 wt. % fluid, about 15 wt. %fluid, about 20 wt. % fluid, or any ranges therebetween. In someaspects, the weight ratio of purge fluid to polymer flake in theconcentrated stream is from about 0.005 to about 1, for example about0.005, about 0.01, about 0.02, about 0.05, about 0.1, about 0.3, about0.4, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1, orany ranges therebetween.

In some aspects, the process further includes passing the concentratedstream to a first degassing chamber, wherein a first purge fluidincluding one or more light hydrocarbons contacts the concentratedstream to produce a partially degassed polymer flake stream and a purgefluid stream. The partially degassed polymer flake stream includes thefluid in a lower concentration than in the concentrated stream and thepurge fluid stream includes the solid polymer flake in a lowerconcentration than in the concentrated stream. In some aspects, thepartially degassed polymer flake stream contains less than 1 wt. %fluid, less than about 0.1 wt. % fluid, or less than about 0.01 wt. %fluid, for example about 1 wt. % fluid, about 0.9 wt. % fluid, about 0.8wt. % fluid, about 0.7 wt. % fluid, about 0.6 wt. % fluid, about 0.5 wt.% fluid, about 0.4 wt. % fluid, about 0.3 wt. % fluid, about 0.2 wt. %fluid, about 0.1 wt. % fluid, about 0.09 wt. % fluid, about 0.08 wt. %fluid, about 0.07 wt. % fluid, about 0.06 wt. % fluid, about 0.05 wt. %fluid, about 0.04 wt. % fluid, about 0.03 wt. % fluid, about 0.02 wt. %fluid, about 0.01 wt. % fluid, or any ranges therebetween. In someaspects, the purge fluid stream contains less than 1 wt. % solid polymerflake, or less than 0.1 wt. % solid polymer flake, for example about 1wt. % solid polymer flake, about 0.9 wt. % solid polymer flake, about0.8 wt. % solid polymer flake, about 0.7 wt. % solid polymer flake,about 0.6 wt. % solid polymer flake, about 0.5 wt. % solid polymerflake, about 0.4 wt. % solid polymer flake, about 0.3 wt. % solidpolymer flake, about 0.2 wt. % solid polymer flake, about 0.1 wt. %solid polymer flake, about 0.09 wt. % solid polymer flake, about 0.08wt. % solid polymer flake, about 0.07 wt. % solid polymer flake, about0.06 wt. % solid polymer flake, about 0.05 wt. % solid polymer flake,about 0.04 wt. % solid polymer flake, about 0.03 wt. % solid polymerflake, about 0.02 wt. % solid polymer flake, about 0.01 wt. % solidpolymer flake, or any ranges therebetween. In some aspects, the purgefluid stream contains at least 0.1 wt. % fluid or at least 1 wt. %fluid, for example about 0.1 wt. % fluid, about 0.5 wt. % fluid, about 1wt. % fluid, about 5 wt. % fluid, about 10 wt. % fluid, about 15 wt. %fluid, about 20 wt. % fluid, or any ranges therebetween. In someaspects, the weight ratio of purge fluid to polymer flake in theconcentrated stream is from about 0.005 to about 1, for example about0.005, about 0.01, about 0.02, about 0.05, about 0.1, 0.3, about 0.4,about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1, or anyranges therebetween.

In some aspects, the first degassing chamber has a residence time offrom about 30 minutes to about 180 minutes, for example about 30minutes, about 40 minutes, about 50 minutes, about 60 minutes, about 70minutes, about 80 minutes, about 90 minutes, about 100 minutes, about110 minutes, about 120 minutes, about 130 minutes, about 140 minutes,about 150 minutes, about 160 minutes, about 170 minutes, about 180minutes, or any ranges therebetween. For example, in some aspects, thefirst degassing chamber has a residence time of from about 30 minutes toabout 60 minutes, or from about 35 minutes to about 50 minutes.

In some aspects, the purge fluid is heated before being introduced intothe first degassing chamber. However, without intending to be bound byany particular theory, it is believed that heating the purge fluid isnot required. Specifically, it is believed that the higher specific heatof the purge fluid compared to pure nitrogen fluid allows for effectivedegassing of the solid polymer flake without preheating of the purgefluid.

In some aspects, the first degassing chamber is at about 0 psig. Withoutintending to be bound by any particular theory, it is believed that apressure at about vacuum improves equilibrium at the same mass strippingrate as compared to a first degassing chamber at a pressure abovevacuum. In some aspects, the pressure within the first degassing chamberis from about 1 psig to about 10 psig, for example about 1 psig, about 2psig, about 3 psig, about 4 psig, about 5 psig, about 6 psig, about 7psig, about 8 psig, about 9 psig, about 10 psig, and any rangestherebetween. In some aspects, the first degassing chamber is from about150 psig to about 300 psig, for example about 150 psig, about 160 psig,about 170 psig, about 180 psig, about 190 psig, about 200 psig, about210 psig, about 220 psig, about 230 psig, about 240 psig, about 250psig, about 260 psig, about 270 psig, about 280 psig, about 290 psig,about 300 psig, or any ranges therebetween. Without intending to bebound by any particular theory, it is believed that a first degassingchamber at a higher pressure may result in less energy being required topump the purge stream back to the polymerization reactor.

In some aspects, the first degassing chamber is operated so that theconcentration of heavy hydrocarbons (HHC) in the purge fluid leaving thefirst degassing chamber does not reach equilibrium with the concentratedstream of polymer flake entering the first degassing chamber. As usedherein, a “G/P ratio” is used to refer to the mass flow rate of purgegas stream fed to the first degassing chamber (G) divided by the massflow rate of the concentrated stream of polymer flake (P).

While not intending to be bound by any particular theory, in someaspects, the minimum G/P ratio in the first degassing chamber is the G/Pratio at which the HHC concentration in the purge stream leaving thepurge column has increased to the point that it is in equilibrium withthe concentrated stream at the HHC concentration of the concentratedsteam and at the conditions (temperature and pressure) of the firstdegassing chamber. Operating the first degassing chamber at above theminimum G/P ratio assures that equilibrium between the purge stream andthe solid polymer flake continually decreases the HHC concentration atthe surface of the solid polymer flake as the solid polymer flakeprogresses through the first degassing chamber. The minimum G/P ratiocan be estimated by the following formula:

$\frac{\{ {\frac{({HHC})_{in}}{\lbrack E\rbrack_{in}} - ({HHC})_{in}} \}*D_{g}}{P} = ( {{minimum}\mspace{14mu}\frac{G}{P}\mspace{14mu}{ratio}} )$wherein HHC_(in) is the volume rate at which the one or more heavyhydrocarbons are fed to the first degassing chamber (ft³ per minute)from all streams (including both the concentrated polymer flake streamand purge fluid stream), [E]_(in) is the molar concentration of one ormore HHC's in the purge fluid leaving the first degassing stream thatwould be in equilibrium with the concentrated polymer flake stream,D_(g) is the density of the purge fluid stream at the conditions of thefirst degassing chamber, and P is the mass rate of the concentratedpolymer flake stream. In some aspects, the first degassing chamber isoperated at a G/P ratio of between 1 and 2 times the minimum G/P ratio.

In some aspects, the first degassing chamber is operated at a G/P ratioof at least 2 times the minimum G/P ratio. For example, in some aspects,the first degassing chamber is operated at a G/P ratio of about 2 timesthe minimum, about 3 times the minimum, about 4 times the minimum, about5 times the minimum, about 6 times the minimum, about 7 times theminimum, about 8 times the minimum, about 9 times the minimum, about 10times the minimum, or any ranges therebetween. Without intending to bebound by any particular theory, it is believed that G/P ratios of lessthan 2 require increased residence time and vessel size of the firstdegassing chamber. Without intending to be bound by any particulartheory, it is believed that G/P ratios of more than 4 or 5 times theminimum G/P ratio may require higher purge fluid stream rates, withoutsignificantly decreasing the required residence time or vessel size.

Without intending to be bound by any particular theory, it is believedthat the chamber size of the first degassing chamber may be minimized byoperating at from about 2 to about 5 times the minimum G/P ratio.Without intending to be bound by any particular theory, it is believedthat operating the first degassing chamber at from about 2 to about 5times the minimum G/P ratio may allow a particular HHC concentration tobe reached in the partially degassed stream within between 1.5 and 4times the minimum residence time. Without intending to be bound by anyparticular theory, it is believed that, as the G/P ratio approaches theminimum G/P ratio, the residence time required to achieve a particularHHC concentration in the partially degassed stream can become infinitelylarge.

In some aspects, the first degassing chamber is substantiallycylindrical, and has a ratio of length to diameter of from about 4:1 to8:1. In some aspects, the inner diameter of the first degassing chamberis from about 5 feet to about 6 feet. In some aspects, the concentratedstream flows through the degassing chamber in plug flow. In someaspects, the superficial velocity of the purge gas entering the firstdegassing chamber is about 90% or less of the minimum fluidizationvelocity, for example about 90% of the minimum fluidization velocity,about 80% of the minimum fluidization velocity, about 70% of the minimumfluidization velocity, about 60% of the minimum fluidization velocity,about 50% of the minimum fluidization velocity, about 40% of the minimumfluidization velocity, about 30% of the minimum fluidization velocity,about 20% of the minimum fluidization velocity, about 10% of the minimumfluidization velocity, or any ranges therebetween.

In some aspects, the purge fluid is added to the first degassing chamberat a point which is less than about 20% along the length of the firstdegassing chamber, in the direction of the flow of the purge fluid, forexample at a point which is about 19% along the length of the firstdegassing chamber, about 15% along the length of the first degassingchamber, about 10% along the length of the first degassing chamber,about 5% along the length of the first degassing chamber, about 0% alongthe length of the first degassing chamber, or any ranges therebetween.

In some aspects, the flash chamber and the first degassing chamber areboth within a single piece of equipment. For example, in some aspects,the flash chamber may be located at one end of or above a plug flow bedof polymer flake, and the degassing chamber may be the remainder of theplug flow bed.

In some aspects, the purge fluid stream is recycled to thepolymerization reactor. In some aspects, the purge fluid stream isrecycled to the polymerization reactor without further separation orpurification steps. In some aspects, the purge fluid is added to thefirst degassing chamber at more than one location along the firstdegassing chamber.

In some aspects, the system further includes a second degassing chamberconfigured to produce a fully degassed polymer flake stream bycontacting the partially degassed polymer flake stream with a secondpurge stream comprising nitrogen to produce the fully degassed polymerflake stream and a used nitrogen stream. The fully degassed polymerflake stream includes the fluid and light hydrocarbons at a lowerconcentration than in the partially degassed polymer flake stream andthe used nitrogen stream includes the heavy and light hydrocarbons fromthe partially degassed stream at a concentration greater than the secondpurge stream. In some aspects, the fully degassed polymer flake streamincludes light and heavy hydrocarbons at less than 100 ppmw (parts permillion by weight), less than 20 ppmw, less than 10 ppmw, or less than 5ppmw, for example about 100 ppmw, about 90 ppmw, about 80 ppmw, about 70ppmw, about 60 ppmw, about 50 ppmw, about 40 ppmw, about 30 ppmw, about20 ppmw, about 15 ppmw, about 10 ppmw, about 9 ppmw, about 8 ppmw, about7 ppmw, about 6 ppmw, about 5 ppmw, about 4 ppmw, about 3 ppmw, about 2ppmw, about 1 ppmw, or any ranges therebetween. In some aspects, thefully degassed polymer flake stream in stagnant air will generate ahydrocarbon concentration of less than 50% LEL (lower explosive limit),less than 20% LEL, or less than 10% LEL, for example about 50% LEL,about 45% LEL, about 40% LEL, about 35% LEL, about 30% LEL, about 25%LEL, about 20% LEL, about 15% LEL, about 10% LEL, about 9% LEL, about 8%LEL, about 7% LEL, about 6% LEL, about 5% LEL, about 4% LEL, about 3%LEL, about 2% LEL, about 1% LEL, or any ranges therebetween. In someaspects, the weight ratio of the second purge fluid to the polymer flakein the partially degassed stream is from about 0.001 to about 0.03, forexample about 0.001, about 0.005, about 0.01, about 0.02, about 0.025,about 0.03, or any ranges therebetween.

In some aspects, the process further includes passing the partiallydegassed polymer flake stream to a second degassing chamber, wherein asecond purge fluid including nitrogen contacts the partially degassedpolymer flake stream to produce a fully degassed polymer flake streamand a used nitrogen stream. The fully degassed polymer flake streamincludes the fluid and light hydrocarbons at a lower concentration thanin the partially degassed polymer flake stream and the used nitrogenstream includes the heavy and light hydrocarbons from the partiallydegassed stream at a concentration greater than the second purge streamIn some aspects, the fully degassed polymer flake stream includes lightand heavy hydrocarbons at less than 100 ppmw, less than 20 ppmw, lessthan 10 ppmw, or less than 5 ppmw, for example about 100 ppmw, about 90ppmw, about 80 ppmw, about 70 ppmw, about 60 ppmw, about 50 ppmw, about40 ppmw, about 30 ppmw, about 20 ppmw, about 15 ppmw, about 10 ppmw,about 9 ppmw, about 8 ppmw, about 7 ppmw, about 6 ppmw, about 5 ppmw,about 4 ppmw, about 3 ppmw, about 2 ppmw, about 1 ppmw, or any rangestherebetween. In some aspects, the fully degassed polymer flake streamin stagnant air will generate a hydrocarbon concentration of less than50% LEL, less than 20% LEL, or less than 10% LEL, for example about 50%LEL, about 45% LEL, about 40% LEL, about 35% LEL, about 30% LEL, about25% LEL, about 20% LEL, about 15% LEL, about 10% LEL, about 9% LEL,about 8% LEL, about 7% LEL, about 6% LEL, about 5% LEL, about 4% LEL,about 3% LEL, about 2% LEL, about 1% LEL, or any ranges therebetween. Insome aspects, the weight ratio of the second purge fluid to the polymerflake in the partially degassed stream is from about 0.001 to about0.03, for example about 0.001, about 0.005, about 0.01, about 0.02,about 0.025, about 0.03, or any ranges therebetween. In some aspects,the second degassing chamber has a residence time of from about 5minutes to about 180 minutes, for example about 5 minutes, about 10minutes, about 20 minutes, about 30 minutes, about 40 minutes, about 50minutes, about 60 minutes, about 70 minutes, about 80 minutes, about 90minutes, about 100 minutes, about 110 minutes, about 120 minutes, about130 minutes, about 140 minutes, about 150 minutes, about 160 minutes,about 170 minutes, about 180 minutes, or any ranges therebetween. Forexample, in some aspects, the second degassing chamber has a residencetime of from about 30 minutes to about 60 minutes, or from about 35minutes to about 50 minutes. In some aspects, the second degassingchamber has a residence time of from about 5 minutes to about 15minutes, for example about 5 minutes, about 6 minutes, about 7 minutes,about 8 minutes, about 9 minutes, about 10 minutes, about 11 minutes,about 12 minutes, about 13 minutes, about 14 minutes, about 15 minutes,or any ranges therebetween.

In some aspects, the G/P ratio of the second degassing chamber issufficient to remove the purge fluid to a desired level. Withoutintending to be bound by any particular theory, it is believed that thepurge fluid will be much easier to remove from the solid polymer flakethan the one or more heavy hydrocarbons, since it is believed that theequilibrium between the purge fluid will favor removing the purge fluidfrom the solid polymer flake. While not intending to be bound by anyparticular theory, in some aspects, the minimum G/P ratio in the seconddegassing chamber is the ratio of the mass rate of interstitial gasbeing transferred to the second gas chamber to the weight rate of solidpolymer flake being transferred to the second gas chamber. Withoutintending to be bound by any particular theory, it is believed that thevolume rate of interstitial gas being transferred to the seconddegassing chamber can be calculated as follows:

$R_{interstitial} = {V_{flake}*( {1 - \frac{SBD}{D}} )}$wherein R_(interstitial) is the volume rate of interstitial gas,V_(flake) is the volume rate of solid polymer flake being transferred tothe second degassing chamber, SBD is the settled bulk density, and D isthe density of the solid polymer flake. The minimum mass rate of purgefluid to the second degassing chamber is then calculated by multiplyingthe volume rate of interstitial gas by the density of the purge fluid atthe conditions in the second degassing chamber.

In some aspects, the G/P ratio in the second degassing chamber is fromabout 2 times the minimum G/P ratio to about 10 times the minimum G/Pratio. In some aspects, the G/P ratio in the second degassing chamber isfrom about 1 times the minimum G/P ratio to about 30 times the minimumG/P ratio

In some aspects, the second degassing chamber is substantiallycylindrical, and has a ratio of length to diameter of from about 4:1 to8:1. In some aspects, the inner diameter of the second degassing chamberis from about 5 feet to about 6 feet. In some aspects, the concentratedstream flows through the first degassing chamber in plug flow.

In some aspects, the superficial velocity of the second purge gasentering the second degassing chamber is about 90% or less of theminimum fluidization velocity, for example about 90% of the minimumfluidization velocity, about 80% of the minimum fluidization velocity,about 70% of the minimum fluidization velocity, about 60% of the minimumfluidization velocity, about 50% of the minimum fluidization velocity,about 40% of the minimum fluidization velocity, about 30% of the minimumfluidization velocity, about 20% of the minimum fluidization velocity,about 10% of the minimum fluidization velocity, or any rangestherebetween.

In some aspects, the first degassing chamber and the second degassingchamber have a combined residence time of from about 30 minutes to about180 minutes, for example about 30 minutes, about 40 minutes, about 50minutes, about 60 minutes, about 70 minutes, about 80 minutes, about 90minutes, about 100 minutes, about 110 minutes, about 120 minutes, about130 minutes, about 140 minutes, about 150 minutes, about 160 minutes,about 170 minutes, about 180 minutes, or any ranges therebetween. Forexample, in some aspects, the first degassing chamber and the seconddegassing chamber have a combined residence time of from about 30minutes to about 60 minutes, or from about 35 minutes to about 50minutes. For example, in some aspects, the first degassing chamber has aresidence time of from about 10 minutes to about 170 minutes and thesecond degassing chamber has a residence time of from about 170 minutesto about 10 minutes.

In some aspects, the second purge fluid is added to the second degassingchamber at a point which is less than about 20% along the length of thesecond degassing chamber, in the direction of the flow of the secondpurge fluid, for example at a point which is about 19% along the lengthof the second degassing chamber, about 15% along the length of thesecond degassing chamber, about 10% along the length of the seconddegassing chamber, about 5% along the length of the second degassingchamber, about 0% along the length of the second degassing chamber, orany ranges therebetween.

In some aspects, the used nitrogen stream is further passed to aseparation process to separate any light hydrocarbons from the usednitrogen stream and produce a purified nitrogen stream and a hydrocarbonstream. The hydrocarbon stream contains the light hydrocarbons in aconcentration higher than in the used nitrogen stream, and the purifiednitrogen stream contains the light hydrocarbons in a concentration lowerthan in the used nitrogen stream. In some aspects, the purified nitrogenis recycled to the second degassing chamber. In some aspects, thehydrocarbon stream is recycled to the polymerization reactor. In someaspects, the hydrocarbon stream is sent to a flare.

ILLUSTRATED ASPECTS

FIG. 1 is a schematic illustration of a system or process 100 accordingto aspects of the present disclosure. A reactant stream 101 is providedto a polymerization reactor 103 which produces a product stream 105containing solid polymer flake entrained in a fluid. The product stream105 is provided to a flash chamber 107 configured to separate the solidpolymer flake from the fluid, producing a fluid stream 109 and aconcentrated stream 111. The fluid stream 109 contains the solid polymerflake in a lower concentration than in the product stream 105, and theconcentrated stream 111 contains the solid polymer flake in a higherconcentration than in the product stream 105. Next, the concentratedstream 111 and a purge fluid 115 are fed to a first degassing chamber113 configured to separate the concentrated stream 111 into a partiallydegassed stream 117 and a purge fluid stream 119. The purge fluid stream119 contains the solid polymer flake in a lower concentration than theconcentrated stream 111, and the partially degassed stream 117 containsthe fluid in a lower concentration than in the concentrated stream 111.The fluid stream 109 and the purge fluid stream 119 are recycled to thepolymerization reactor 103.

Next, the partially degassed stream 117 and a second purge stream 123which includes nitrogen are fed to a second degassing chamber 121configured to separate the partially degassed stream 117 into a fullydegassed polymer flake stream 125 and a used nitrogen stream 127. Thefully degassed polymer flake stream 125 includes the fluid at a lowerconcentration than in the partially degassed polymer flake stream 117and the used nitrogen stream includes the solid polymer flake in a lowerconcentration than in the partially degassed polymer flake stream 117.

EXAMPLES

The invention is further illustrated by the following examples, whichare not to be construed in any way as imposing limitations to the scopeof this invention. Various other aspects, aspects, modifications, andequivalents thereof which, after reading the description herein, cansuggest themselves to one of ordinary skill in the art without departingfrom the spirit of the present invention or the scope of the appendedclaims.

Prophetic Example 1

A reactant stream is provided to a gas phase polymerization reactorwhich produces linear low density polyethylene at a density of 0.918g/cc. The linear low density polyethylene being produced is a copolymerof ethylene and a heavy hydrocarbon monomer, hexene. A heavy hydrocarbondiluent, n-hexane, is also present in the reactor. The polymerizationreactor is being operated at 86° C. and 315 psia. The gas composition isas follows: 100 psi of ethylene, 10.5 psi of hexane-1, 8.4 psi ofn-hexane, and the balance nitrogen.

A product stream containing solid polymer flakes entrained in a fluid isdischarged continuously from the reactor at a rate of about 75,000lbs/hr of solid polymer flakes. The solid polymer flakes have an averagethickness of 800 microns. The product stream is provided to a flashchamber configured to separate the solid polymer flake from the fluid,producing a fluid stream and a concentrated stream. The average pressurein the flash chamber is controlled at 25 psia and the temperature ismeasured to be 80° C. The fluid stream contains the solid polymer flakein a lower concentration than in the product stream. The fluid stream isfiltered and returned to the reactor using a compressor without furtherpurification or treatment. The concentrated stream contains the solidpolymer flake in a higher concentration than in the product stream. Theconcentrated stream includes approximately 1.6 wt % of heavyhydrocarbons comprised of hexene-1 and n-hexane that are absorbed intothe solid polymer flake. The concentration of heavy hydrocarbons in thesolid polymer flake is estimated using overall and component massbalances around different portions of the unit.

The concentrated stream of solid polymer flake is introduced into thetop of a first degassing chamber. Towards the bottom of the firstdegassing chamber, a purge fluid consisting of purified ethylene at 80°C. is fed at a rate of 2,500 lbs/hr. The average temperature of thesolids in the first degassing chamber is approximately 78° C. and thepressure is controlled at 20 psia. The level of solids in the degassingchamber is maintained such that the purge fluid permeates and risesthrough a bed of the solid polymer flakes. The solid polymer flakes aremoving downward through the bed in plug flow pattern. The purge fluidleaves the top of the bed of solid polymer flakes and is continuouslydischarged from the top of the vessel. The level of solids in the firstdegassing chamber is controlled such that the solid polymer flakes havean average residence time that provides 40 minutes of contact with therising purge fluid. The solid polymer flakes leave the first degassingchamber as a partially degassed stream.

The purge fluid leaving the first degassing chamber and comprised ofethylene and heavy hydrocarbons, is filtered and returned back to thereactor using a compressor. The purge fluid is returned without anyfurther purification or treatment.

Testing indicates that at 78° C. and 20 psia, the heavy hydrocarbons inthe concentrated stream from the flash chamber (1.6 wt % heavyhydrocarbons) would equilibrate with an ethylene purge fluid streamcomprising approximately 24.6 vol % of the heavy hydrocarbons hexane-1and n-hexane. The minimum G/P ratio for the first degassing chamber forthe above conditions is calculated to be approximately 0.016 lb of purgegas per pound of solid polymer flake using the formula below:

$\frac{\{ {\frac{({HHC})_{in}}{\lbrack E\rbrack_{in}} - ({HHC})_{in}} \}*D_{g}}{P} = ( {{minimum}\mspace{14mu}\frac{G}{P}\mspace{14mu}{ratio}} )$

(HHC)_(in) is 4,839 ft³/hr, calculated as follows. 75,000 lbs/hr totalfed to the first degassing chamber*0.016 lb HHC/lb solid=1,200 lbs/hrHHC fed to the first degassing chamber. 1,200 lb/hr HHC fed to the firstdegassing chamber/0.249 lb/ft³ (HHC density at first degassing chamberconditions)=4,839 ft³/hr. [E]_(in) is 24.6 vol. %, and D_(g) is thedensity of the purge fluid at first degassing chamber conditions=0.081lb/ft³. Thus, the minimum G/Pratio={(4839/0.246)−4839}*0.081/75,000=0.016 lb purge fluid/lb solidpolymer flake.

This means the minimum mass rate of purge fluid would be approximately1,200 lbs/hr (75,000 lbs/hr*0.016 lb/lb=1,200 lbs/hr). Therefore, thefirst degassing chamber is operated at a G/P ratio of about 2.1 timesthe minimum G/P ratio (2,500 lbs/hr/1,200 lbs/hr).

The partially degassed stream containing approximately 8 ppm of heavyhydrocarbons comprised of 1-hexene and n-hexane is discharged throughthe bottom of the first degassing chamber.

Next, the partially degassed stream is introduced into the top of asecond degassing chamber. Towards the bottom of the second degassingchamber, a purge fluid consisting of pure nitrogen at 80° C. is fed at arate of 500 lbs/hr. The average temperature of the solids in the seconddegassing chamber is approximately 78° C. and the pressure is controlledat 18 psia. A level of solid polymer flake is maintained in the seconddegassing chamber such that the nitrogen purge fluid permeates and risesthrough the bed of solid polymer flake. The solid polymer flake iscontinuously moving downward through the bed in a plug flow pattern. Thenitrogen purge fluid leaves the top of the bed of solid polymer flakeand is continuously discharged from the top of the vessel as a spentnitrogen stream. The level of solids in the second degassing chamber iscontrolled such that the solid polymer flake has a residence time thatprovides about 10 minutes of contact with the rising purge fluid. Thesolid polymer flakes are discharged from the second degassing chamber asa fully degassed stream.

The spent nitrogen stream from the second degassing column andcomprising nitrogen, ethylene, and small concentrations of heavyhydrocarbon was directed to a hydrocarbon destruction device.

The minimum G/P ratio for the second degassing chamber for the aboveconditions is calculated to be approximately 0.001 lb of nitrogen perpound of solid polymer flake, using the equation above, and theinterstitial volume was calculated using the equation below:

$R_{interstitial} = {V_{flake}*( {1 - \frac{SBD}{D}} )}$

In these calculations, SBD=32 lbs/ft³, D=57 lbs/ft³, V_(flake)=(75,000lbs/hr)/(32 lbs/ft³ settled bulk density)=2,344 ft³/hr.R_(intersticial)=(2,344)*(1-32/57)=1,028 ft³/hr, density of N₂ at 78° F.and 18 psia=0.073 lbs/ft³, min purge gas to second degassingchamber=0.073*1028=75 lbs/hr. Thus, the minimum G/P ratio for the seconddegassing chamber is 75/75000=0.001 lb/lb

Therefore, the second degassing chamber is operated at a G/P ratio ofabout 6.7 times the minimum required G/P ratio (500 lbs/hr/75 lbs/hr).The fully degassed stream contains less than 5 ppm of heavy hydrocarbonsand less than 2 ppm of the light hydrocarbon ethylene.

ASPECTS

The invention is described above with reference to numerous aspects andaspects, and specific examples. Many variations will suggest themselvesto those skilled in the art in light of the above detailed description.All such obvious variations are within the full intended scope of theappended claims. Other aspects of the invention can include, but are notlimited to, the following (aspects typically are described as“comprising” but, alternatively, can “consist essentially of” or“consist of” unless specifically stated otherwise)

In accordance with a first aspect of the present disclosure, a systemfor polymerizing one or more olefin monomers according to a firstaspect, comprising: a polymerization reactor configured to polymerizeone or more olefin monomers and produce a product stream comprisingsolid polymer flake entrained in a fluid; a flash chamber configured toseparate the solid polymer flake from the fluid and to produce a fluidstream and a concentrated stream, wherein the fluid stream comprises thesolid polymer flake in a lower concentration than in the product streamand the concentrated stream comprises the solid polymer flake in ahigher concentration than in the product stream; a first degassingchamber configured to separate the concentrated stream by contacting theconcentrated stream with a purge fluid comprising one or more lighthydrocarbons to produce a partially degassed polymer flake stream and apurge fluid stream, wherein the partially degassed polymer flake streamcomprises the fluid in a lower concentration than in the concentratedstream and the purge fluid stream comprises the solid polymer flake in alower concentration than in the concentrated stream.

In accordance with a second aspect of the present disclosure, the systemof the first aspect is described, wherein the fluid stream contains lessthan about 5 wt. % solid polymer flake and the concentrated streamcontains more than about 80 wt. % solid polymer flake.

In accordance with a third aspect of the present disclosure, the systemof any one of the first or second aspects is described, wherein thepartially degassed polymer flake stream contains less than about 1 wt. %fluid and the purge fluid stream contains less than about 1 wt. % solidpolymer flake.

In accordance with a fourth aspect of the present disclosure, the systemof any one of the first to third aspects is described, wherein the flashchamber and the first degassing chamber are both within a single pieceof equipment.

In accordance with a fifth aspect of the present disclosure, the systemof any one of the first to fourth aspects is described, furthercomprising a second degassing chamber configured to produce a fullydegassed polymer flake stream by contacting the partially degassedpolymer flake stream with a second purge stream comprising nitrogen toproduce the fully degassed polymer flake stream and a used nitrogenstream, wherein the fully degassed polymer flake stream comprises thefluid at a lower concentration than in the partially degassed polymerflake stream and the used nitrogen stream comprises the solid polymerflake in a lower concentration than in the partially degassed polymerflake stream.

In accordance with a sixth aspect of the present disclosure, the systemof the fourth aspect is described, wherein the fully degassed polymerflake stream contains less than about 100 ppmw of the fluid.

In accordance with a seventh aspect of the present disclosure, thesystem of any one of the first to sixth aspects is described, whereinthe fluid comprises at least one of the one or more olefin monomers.

In accordance with a eighth aspect of the present disclosure, the systemof any one of the first to seventh aspects is described, wherein thefluid is a gas.

In accordance with a ninth aspect of the present disclosure, the systemof any one of the first to seventh aspects is described, wherein thefluid is a liquid.

In accordance with a tenth aspect of the present disclosure, the systemof any one of the first to seventh aspects is described, wherein thepolymerization reactor comprises a gas phase reactor.

In accordance with an eleventh aspect of the present disclosure, thesystem of any one of the first to seventh or ninth aspects is described,wherein the polymerization reactor comprises a liquid phase reactor.

In accordance with a twelfth aspect of the present disclosure, thesystem of the eleventh aspect is described, wherein the liquid phasereactor is a loop slurry reactor or an autoclave reactor.

In accordance with a thirteenth aspect of the present disclosure, thesystem of any one of the first to twelfth aspects is described, whereinthe purge fluid stream is recycled to the polymerization reactor.

In accordance with a fourteenth aspect of the present disclosure, thesystem of any one of the first to thirteenth aspects is described,wherein the one or more olefins comprise ethylene and the polymer flakecomprises polyethylene.

In accordance with a fifteenth aspect of the present disclosure, thesystem of any one of the first to fourteenth aspects is described,wherein the polymerization reactor is further configured to polymerizeone or more olefins in the presence of one or more heavy hydrocarbons.

In accordance with a sixteenth aspect of the present disclosure, thesystem of any one of the first to fifteenth aspects is described,wherein the first degassing chamber has a residence time of from about 5minutes to about 180 minutes.

In accordance with a seventeenth aspect of the present disclosure, thesystem of any one of the first to sixteenth aspects is described,wherein the second degassing chamber has a residence time of from about5 minutes to about 180 minutes.

In accordance with an eighteenth aspect of the present disclosure, thesystem of any one of the fifth to fifteenth aspects is described,wherein the first degassing chamber and the second degassing chamberhave a combined residence time of from about 30 minutes to about 180minutes.

In accordance with a nineteenth aspect of the present disclosure, thesystem of any one of the first to eighteenth aspects is described,wherein the weight ratio of purge fluid to polymer flake in theconcentrated stream is from about 0.005 to about 1.

In accordance with a twentieth aspect of the present disclosure, thesystem of any one of the first to nineteenth aspects is described,wherein the weight ratio of the second purge fluid to the polymer flakein the partially degassed stream is from about 0.001 to about 0.03.

In accordance with a twenty-first aspect of the present disclosure, aprocess for polymerizing one or more olefin monomers comprising:polymerizing one or more olefin monomers in a polymerization reactor toform a product stream comprising solid polymer flake entrained in afluid; passing the product stream to a flash chamber to produce a fluidstream and a concentrated stream of polymer flake entrained in thefluid, wherein the fluid stream comprises the solid polymer flake in alower concentration than in the product stream and the concentratedstream comprises the solid polymer flake in a higher concentration thanin the product stream; passing the concentrated stream to a firstdegassing chamber, wherein a first purge fluid comprising one or morelight hydrocarbons contacts the concentrated stream to produce apartially degassed polymer flake stream and a purge fluid stream whereinthe partially degassed polymer flake stream comprises the fluid in alower concentration than in the concentrated stream and the purge fluidstream comprises the solid polymer flake in a lower concentration thanin the concentrated stream.

In accordance with a twenty-second aspect of the present disclosure, thetwenty-first aspect is described, wherein the fluid stream contains lessthan about 5 wt. % solid polymer flake and the concentrated streamcontains more than about 80 wt. % solid polymer flake.

In accordance with a twenty-third aspect of the present disclosure, thesystem of any one of the twenty-first or twenty-second aspects isdescribed, wherein the partially degassed polymer flake stream containsless than about 1 wt. % fluid and the purge fluid stream contains lessthan about 1 wt. % solid polymer flake.

In accordance with a twenty-fourth aspect of the present disclosure, thesystem of any one of the twenty-first to twenty-third aspects isdescribed, further comprising passing the partially degassed polymerflake stream to a second degassing chamber, wherein a second purge fluidcomprising nitrogen contacts the partially degassed polymer flake streamto produce a fully degassed polymer flake stream and a used nitrogenstream, wherein the fully degassed polymer flake stream comprises thefluid at a lower concentration than in the partially degassed polymerflake stream and the used nitrogen stream comprises the solid polymerflake in a lower concentration than in the partially degassed polymerflake stream.

In accordance with a twenty-fifth aspect of the present disclosure, thesystem of the twenty-fourth aspect is described, wherein the fullydegassed polymer flake stream contains less than about 100 ppmw of thefluid.

In accordance with a twenty-sixth aspect of the present disclosure, thesystem of any one of the twenty-first to twenty-fifth aspects isdescribed, wherein the fluid comprises at least one of the one or moreolefin monomers.

In accordance with a twenty-seventh aspect of the present disclosure,the system of any one of the twenty-first to twenty-sixth aspects isdescribed, wherein the fluid is a gas.

In accordance with a twenty-eighth aspect of the present disclosure, thesystem of any one of the twenty-first to twenty-sixth aspects isdescribed, wherein the fluid is a liquid.

In accordance with a twenty-ninth aspect of the present disclosure, thesystem of any one of the twenty-first to twenty-seventh aspects isdescribed, wherein the polymerization reactor comprises a gas phasereactor.

In accordance with a thirtieth aspect of the present disclosure, thesystem of any one of the twenty-first to twenty-sixth or twenty-eighthaspects is described, wherein the polymerization reactor comprises aliquid phase reactor.

In accordance with a thirty-first aspect of the present disclosure, thesystem of the thirtieth aspect is described, wherein the liquid phasereactor is a loop slurry reactor or an autoclave reactor.

In accordance with a thirty-second aspect of the present disclosure, thesystem of any one of the twenty-first to thirty-first aspects isdescribed, further comprising recycling the purge fluid stream to thepolymerization reactor.

In accordance with a thirty-third aspect of the present disclosure, thesystem of any one of the twenty-first to thirty-second aspects isdescribed, wherein the one or more olefins comprise ethylene and thepolymer flake comprises polyethylene.

In accordance with a thirty-fourth aspect of the present disclosure, thesystem of any one of the twenty-first to thirty-third aspects isdescribed, further comprising polymerizing the one or more olefins inthe presence of one or more heavy hydrocarbons.

In accordance with a thirty-fifth aspect of the present disclosure, thesystem of any one of the twenty-first to thirty-fourth aspects isdescribed, wherein the first degassing chamber has a residence time offrom about 5 minutes to about 180 minutes.

In accordance with a thirty-sixth aspect of the present disclosure, thesystem of any one of the twenty-fourth to thirty-fifth aspects isdescribed, wherein the second degassing chamber has a residence time offrom about 5 minutes to about 180 minutes.

In accordance with a thirty-seventh aspect of the present disclosure,the system of any one of the twenty-fourth to thirty-fourth aspects isdescribed, wherein the first degassing chamber and the second degassingchamber have a combined residence time of from about 30 minutes to about180 minutes.

In accordance with a thirty-eighth aspect of the present disclosure, thesystem of any one of the twenty-first to thirty-seventh aspects isdescribed, wherein the weight ratio of purge fluid to polymer flake inthe concentrated stream is from about 0.005 to about 1.

In accordance with a thirty-ninth aspect of the present disclosure, thesystem of any one of the twenty-first to thirty eighth aspects isdescribed, wherein the weight ratio of the second purge fluid to thepolymer flake in the partially degassed stream is from about 0.001 toabout 0.03.

What is claimed is:
 1. A system for polymerizing one or more olefinmonomers, comprising: a polymerization reactor configured to polymerizeone or more olefin monomers and produce a product stream comprisingsolid polymer flake entrained in a fluid; a flash chamber configured toseparate the solid polymer flake from the fluid and to produce a fluidstream and a concentrated stream, wherein the fluid stream comprises thesolid polymer flake in a lower concentration than in the product stream,and wherein the concentrated stream comprises the solid polymer flake ina higher concentration than in the product stream; a fluid streamrecycle line configured to recycle the fluid stream from the flashchamber to the polymerization reactor; a first degassing chamberconfigured to separate the concentrated stream by contacting theconcentrated stream with a first purge fluid comprising one or morelight hydrocarbons to produce a partially degassed polymer flake streamand a purge fluid stream, wherein the partially degassed polymer flakestream comprises the fluid in a lower concentration than in theconcentrated stream and the purge fluid stream comprises the solidpolymer flake in a lower concentration than in the concentrated stream,wherein the polymerization reactor, the flash chamber, and the firstdegassing chamber are distinct from each other.
 2. The system of claim1, further comprising a second degassing chamber configured to produce afully degassed polymer flake stream by contacting the partially degassedpolymer flake stream with a second purge fluid comprising nitrogen toproduce the fully degassed polymer flake stream and a used nitrogenstream, wherein the fully degassed polymer flake stream comprises thefluid at a lower concentration than in the partially degassed polymerflake stream and the used nitrogen stream comprises the solid polymerflake in a lower concentration than in the partially degassed polymerflake stream.
 3. The system of claim 1, wherein the first purge fluidcomprises at least one of the one or more olefin monomers.
 4. The systemof claim 1, wherein the fluid is a gas.
 5. The system of claim 1,wherein the fluid is a liquid.
 6. The system of claim 1, furthercomprising a first purge recycle line configured to recycle the purgefluid stream from the first degassing chamber to the polymerizationreactor.
 7. The system of claim 1, wherein the one or more olefinmonomers comprises ethylene and the polymer flake comprisespolyethylene.
 8. The system of claim 1, wherein the polymerizationreactor is further configured to polymerize one or more olefin monomersin the presence of one or more heavy hydrocarbons.
 9. The system claim1, wherein the first degassing chamber has a residence time of fromabout 30 minutes to about 180 minutes.
 10. The system of claim 1,wherein the second degassing chamber has a residence time of from about30 minutes to about 180 minutes.
 11. The system of claim 1, wherein aweight ratio of the first purge fluid to the solid polymer flake in theconcentrated stream is from about 0.005 to about
 1. 12. The system ofclaim 1, wherein a weight ratio of the second purge fluid to the solidpolymer flake in the partially degassed polymer flake stream is fromabout 0.001 to about 0.03.
 13. The system of claim 1, wherein the firstdegassing chamber has a length, and wherein an introduction point of thefirst purge fluid is less than about 20% along the length of the firstdegassing chamber, in the direction of the flow of the first purgefluid.
 14. A process for polymerizing one or more olefin monomerscomprising: polymerizing one or more olefin monomers in a polymerizationreactor to form a product stream comprising solid polymer flakeentrained in a fluid; passing the product stream to a flash chamber toproduce a fluid stream and a concentrated stream of solid polymer flakeentrained in the fluid, wherein the fluid stream comprises the solidpolymer flake in a lower concentration than in the product stream andthe concentrated stream comprises the solid polymer flake in a higherconcentration than in the product stream; recycling the fluid streamfrom the flash chamber to the polymerization reactor; passing theconcentrated stream to a first degassing chamber, wherein a first purgefluid comprising one or more light hydrocarbons contacts theconcentrated stream to produce a partially degassed polymer flake streamand a purge fluid stream wherein the partially degassed polymer flakestream comprises the fluid in a lower concentration than in theconcentrated stream and the purge fluid stream comprises the solidpolymer flake in a lower concentration than in the concentrated stream;passing the partially degassed polymer flake stream to a seconddegassing chamber, wherein a second purge fluid comprising nitrogencontacts the partially degassed polymer flake stream to produce a fullydegassed polymer flake stream and a used nitrogen stream, wherein thefully degassed polymer flake stream comprises the fluid at a lowerconcentration than in the partially degassed polymer flake stream andthe used nitrogen stream comprises the solid polymer flake in a lowerconcentration than in the partially degassed Polymer flake stream,wherein a weight ratio of the second purge fluid to the solid polymerflake in the partially degassed polymer flake stream is from about 0.001to about 0.03.
 15. The process of claim 14, wherein the first purgefluid consists essentially of ethylene.
 16. The process of claim 15,wherein the fluid comprises at least one of the one or more olefinmonomers.
 17. The process of claim 15, wherein the fluid is a gas. 18.The process of claim 15, wherein the fluid is a liquid.
 19. The processof claim 15, further comprising recycling the first purge fluid streamto the polymerization reactor.
 20. The process of claim 15, wherein aweight ratio of the first purge fluid to the solid polymer flake in theconcentrated stream is from about 0.005 to about 1.